Runway QDM Information

[roadrabbit]

:(

 

Using the CDU <Divert> you can get much information for nearest airfields to your position. Included, where available, is the ILS frequency for each airfield runway in DCSW. Why no QDM - or am I missing a trick here?

[IdleBoards]

What is QDM?

[roadrabbit]

QDM decoded

 

:huh:

 

With all the other 'Q' codes being flashed around I foolishly assumed .........

 

The QDM of a runway is the magnetic track direction of the runway. Hence it is what you set on the HSI when doing an ILS approach. Hence my question - if you didn't have the airfield chart with you, how would you know the direction of the runway. Modern RW aircraft have all relevant information stored within the CDU computer, including runway length.

 

Generally a QDM is the magnetic track ('course' in North America!) from the aircraft position to a reference point, usually a radio beacon, airfield or, when doing AAR, to the tanker.

[Tetra]

Runway numbers are magnetic heading rounded to the nearest 10. Runway 11 would be heading 110, runway 31, 310 etc.

[IdleBoards]

Oh, I see...Its weird that I've never heard anyone call it that before, especially with as many international students as I've had. Here in 'Merica we just say Approach Course. Its exceedingly rare for anyone to use a Q-code for anything over here (especially the QNE/QNH/QFE buffoonery). Learn something new every day..

 

Anyway, there are some gaps in capability between the A-10's CDU and other modern FMSs. You might also notice that the A-10 has no provision for measured or predictive fuel consumption; aircraft performance; weight & balance; conditional waypoints; etc... So I'd hesitate to compare it directly to another box (giggety).

 

More directly, the DIVERT page is there to save your ass with a bearing and distance to an emergency piece of concrete in day/VMC when NORDO. Everything else is just gravy. Knowing the runway ID is sufficient to set the approximate course on the HSI.

 

Also, dont forget that fighter sorties are briefed to far more rigorous standards than your typical airline flight. The planning is meticulous, and besides all the tactical stuff, also covers divert fields (runway length, approaches, barriers, live/hung ordnance procedures, transient alert supoort, etc.), divert profiles (snap bearing and distance to the divert field from the target/training area, climb profile, ITT/RPM setting, descent profile, bingo fuel, etc.), as well as weather recall and route abort criteria, and so on.

 

Its far more detailed than simply having an alternate listed on the flightplan, and then relying on the FMS to get you there in the event of an emergency. There is little doubt in a fighter pilot's head where he would go in the event of an emergency, and the details of the airfield would have been thoroughly reviewed and briefed.

[roadrabbit]

:thumbup:

 

Spot on - but if you experiment with the various airfields in DCS you will find differences of up to 8 degs between runway ID (or 'number') and the actual QDM (just as can happen in the RW).

 

When scanning instruments in cloud (IFR conditions) with wind effects, the difference can be misleading. If there is no wind it's good to have the ILS or TACAN indicator bar 'vertical' when you are 'on track'. It means you should not slide off the correct heading to maintain the desired track.

 

Similarly, when you have a cross-wind effect, the angle between the track indicator and the vertical on the HSI will be the same as the drift angle when on the correct heading. Thus the presentation again makes sense.

 

To make the point completely obvious - you would never want the ILS localiser presentation at 90 degs i.e. from the 3 o'clock to 9 o'clock position. It would make it virtually impossible to use. Try it and see! :D

[roadrabbit]

:)

 

[ Quote: "Its far more detailed than simply having an alternate listed on the flightplan, and then relying on the FMS to get you there in the event of an emergency. There is little doubt in a fighter pilot's head where he would go in the event of an emergency, and the details of the airfield would have been thoroughly reviewed and briefed."]

 

I take your point, although in my career the briefing was a bit more thorough than perhaps you imply.

 

We also had to divert from anywhere along a route, sometimes up to 14 hours in length, and over what we termed 'desert' (this included the oceans!). This meant that it was impossible to brief for every possible eventuality. The weather could also change dramatically over the period of the flight, thus rendering planned alternates less than useful. Thus at any enforced divert points we wanted a quick means to bring up what the A-10C CDU does in its limited way.

 

Don't get me wrong - I'm not complaining. I am just exploring those limitations so that I know what I can do, what is possible to do, and what is not possible. Always fun to learn :smartass:

[IdleBoards]

...if you experiment with the various airfields in DCS you will find differences of up to 8 degs between runway ID (or 'number') and the actual QDM (just as can happen in the RW).

 

True. Unfortunately, this is a known DCS issue that will (likely) never be corrected. Although the magnetic variation is simulated reasonably accurately across the map, the airport models are often physically misaligned. Tweaking the variation could fix the issue for some airfields, but would make others worse. It's a no-win situation.

 

Let's hope that Nevada and future maps are built correctly from the start, and avoid the issue completely.

 

When scanning instruments in cloud (IFR conditions) with wind effects, the difference can be misleading.

 

I agree. However, if I began an approach in IMC knowing full well that the course I spun into the HSI was only an approximation, I would adjust my scan accordingly.

 

I take your point, although in my career the briefing was a bit more thorough than perhaps you imply.

 

We also had to divert from anywhere along a route, sometimes up to 14 hours in length...

 

Quoted for truth. And I take your point as well; I oversimplified the comparison.

 

A great amount of planning goes into any airline flight, especially an LROPS/ETOPS flight like you described. Further, I concede that the requirements of NAT/NOPAC/other crossing necessitates a higher than normal degree of SA and coordination.

 

When I made the comparison, I was thinking of the all-too-common, "We're headed to ATL...we've been there twice already today. This'll be a max thrust, flaps 8 takeoff on 22L. Runway heading to three thousand then radar vectors to SNOOZ. Clear left. Any questions?" type of briefing.

 

I'm exaggerating again, but you know what I mean.

 

Always fun to learn :smartass:

 

:thumbup:

[Leto]

The QDM of a runway is the magnetic track direction of the runway

You got that wrong, mate. QDM is magnetic bearing from the a/c to the radio station, QDR is the magnetic bearing from the station to the a/c.
Edited August 4, 2013 by Leto

[Hamblue]

You might also notice that the A-10 has no provision for measured or predictive fuel consumption

Guess it doesn't matter. The "World" is so small that if you take off with 100% fuel you can pretty much fly anywhere.

[Fish]

Hmm,

Ive made my own list some time back from sitting on the runway end aligning the aircraft, and tune the HSI. Good to the nearest degree. Its easy to do, just make a flyable on the editor, move it and jump in.

 

Generally I don't have to refer to it, as i'm returning to the same take off base/runway, and i've done my pre-take off checks carefully.

[roadrabbit]

You got that wrong, mate. QDM is magnetic bearing from the a/c to the radio station, QDR is the magnetic bearing from the station to the a/c.

Yes - quite right! I don't know how that slipped in (old age, I guess), but the bit before actually states what you have correctly stated.

 

To take it a bit further, in a past life we DID refer to the the inbound instrument approach track (course) to a runway as the "runway QDM", whether it was strictly according to the definition of QDM or not. It was quicker than saying "inbound instrument approach track" ;-)

Edited August 6, 2013 by roadrabbit

[Suchacz]

VFR airport charts are included in your kneeboard and in DCS World/Docs. Runway directions are there with other info. The charts are also sufficient for instrument approach, but not for true IFR.

[roadrabbit]

VFR airport charts are included in your kneeboard and in DCS World/Docs. Runway directions are there with other info. The charts are also sufficient for instrument approach, but not for true IFR.

 

:thumbup: Agreed, but there are some errors. Nalchik, for example, has the ILS down as being for runway 06, instead of runway 24. Also the runway inbound direction for runway 24 is given as 235, whereas if you line up on the runway 24 for take-off you will see that it is actually 228. :book:

[PFunk1606688187]

Nice to see Fish posting again. :D

[Leto]

:thumbup: Agreed, but there are some errors. Nalchik, for example, has the ILS down as being for runway 06, instead of runway 24. Also the runway inbound direction for runway 24 is given as 235, whereas if you line up on the runway 24 for take-off you will see that it is actually 228. :book:

 

The charts are perfectly fine. Please consider, that there is a difference depending on the aircraft you are flying. A-10C uses magnetic, therefore use the VAD charts labeled "A-10C". There you'll find the magnetic runway heading of 229°. FC3 planes use true, therefore use the VAD charts labeled "FC3" where the runway heading is 235°.

 

The ground charts have both, magnetic and true (229° for mh, 235°T for true)

 

ILS information is perfectly well, also.

 

Maybe you use different charts? Check your DCS World/Docs/Charts folder for

 

DCS_GND_Charts.pdf

DCS_VAD_Charts_A10C.pdf

DCS_VAD_Charts_FC3.pdf

 

provided by http://www.10thGunFighters.de

 

or load them here: http://ariescon.com

Edited August 6, 2013 by Leto

[roadrabbit]

The charts are perfectly fine.

 

Maybe you use different charts? Check your DCS World/Docs/Charts folder for

 

DCS_GND_Charts.pdf

DCS_VAD_Charts_A10C.pdf

DCS_VAD_Charts_FC3.pdf

 

provided by www.10thGunFighters.de

 

or load them here: http://ariescon.com

 

:D Thank you very much! I have been using the wrong charts completely. I have been using the DCS World Airfield Diagrams to which I was pointed.

 

Now I can use the proper approach plates just like I used in a previous life. I learn something new and useful every day - thanks again Leto :thumbup:

[PFunk1606688187]

So you're telling me that if I fly formation in an A-10 with a friend flying an F-15C he'll think we're flying in a different direction?

[Leto]

@Roadrabbit: you are welcome, I am pleased with anyone who makes the effort and uses the charts

 

So you're telling me that if I fly formation in an A-10 with a friend flying an F-15C he'll think we're flying in a different direction?

 

Sure, that's nothing new. Take the example of Nalchik, place DCS and FC3 aircraft "ready to go" on the runway 06. A-10C, Huey etc will indicate a heading of 049° on rwy 06 while F-15, A-10A, Su-33 etc will indicate a heading of 055°. Magnetic vs True. That's the reason for different sets of VAD-charts.

 

On the charts you'll find the variation TN->MN in the lower right corner, in this case 6°

Edited August 7, 2013 by Leto

[roadrabbit]

So you're telling me that if I fly formation in an A-10 with a friend flying an F-15C he'll think we're flying in a different direction?

 

:smilewink: Actually, no he won't. He will know you are both flying in the same direction if you maintain formation. It's just that the 'reading' on his ADI will differ from yours because of the different base reference: yours is magnetic, his is true north. :smartass: